In electrical power distribution, a bus bar is an apparatus that distributes power to multiple connected devices, that conducts electricity within a switchboard, distribution board, substation or other electrical apparatus. The bus bar may be an aluminum or copper conductor supported by insulators that interconnects the loads and the sources of electric power in an electric power system. A typical application is the interconnection of the incoming and outgoing transmission lines and transformers at an electrical substation. Bus bars also interconnect the generator and the main transformers in a power plant. In an industrial plant such as an aluminum smelter, large bus bars supply several tens of thousands of amperes to the electrolytic process.
There are several different types of bus bars. For example, there are rigid bus bars, used at low, medium, and high voltage; strain bus bars, used mainly for high voltage; insulated-phase bus bars, used at medium voltage; and sulfur hexafluoride (SF6)-insulated bus bars, used in medium- and high-voltage systems. The rigid bus-bar is an aluminum or copper bar, which is supported by porcelain insulators. The strain bus-bar is a flexible, stranded conductor which is strung between substation metal structures and held by suspension-type insulators. The insulated-phase bus-bar is a rigid bar supported by insulators and covered by a grounded metal shield. The sulfur hexafluoride-insulated bus-bar is a rigid aluminum tube, supported by insulators and installed in a larger metal tube, which is filled with high-pressure sulfur hexafluoride gas.
One of the challenges in designing a bus bar is accurately estimating the number of connections that may be made with the bus bar. As system and power requirements change, the number of connections to the bus bar may increase.